1. Field of The Invention
This invention relates to cords of the type used in power transmission belts and, more particularly, to an apparatus for pretreating the cords, as by the steps of applying a liquid substance thereto, and curing the substance. The invention is also directed to the method of treating cords through this type of apparatus.
2. Background Art
It is known to use load carrying cords in all types of power transmission belts, i.e. V-belts, V-ribbed belts, toothed belts, etc., and particularly those used in industrial applications. Typically, the cords are made from fiber material, such as polyester fiber, aramid fiber, glass fiber, and the like. To improve adhesion with the belt rubber, it is known to pretreat the fiber cords. For example, it is known to treat the cords with resorcinol formalin latex (RFL) alone or to use the RFL treatment after pretreating the cords with an epoxy or isocyanate compound. It is also known to adhere rubber gum after the RFL treatment.
It is further known to either individually treat a cord or simultaneously treat a plurality of cords by applying a substance thereto and heating the cords to cure the applied substance. In those portions of a treating apparatus in which multiple passes of the cord are required, such as in the heating chamber, guiding rollers for the cords have been arranged in multiple stages so that the cords follow a circuitous path through the heating chamber. For example, the cords may be wrapped in an "S" shape around the various rollers. The multiple cords travel together in substantially parallel relationship through the paths.
With this multiple stage arrangement, the cords are separately threaded on independent sets of rollers to move through an apparatus in parallel relationship with a fixed spacing and are not required to move back and forth in the same plane. This facilitates cord mounting and rethreading of the cords.
However, because of the above multiple stage arrangement, the overall apparatus may be undesirably large. This may result in an increase in the cost of the apparatus, as well as a need for a large amount of operating space, which is often at a premium. This design also has some safety problems associated with setup, maintenance, and periodic cord inspection.
Apparatus for processing a single cord are shown in Japanese Unexamined Patent Publication No. H4-146232 and Japanese Unexamined Patent Publication No. H4-146230. In these apparatus, a cord is directed in a back and forth pattern around a pair of rollers. The single processed cord is wound between the rollers several times and moves axially thereof as the cord is advanced. While these systems eliminate problems associated with multiple stages, they do not permit the simultaneous processing of multiple cords.
Another problem with prior art apparatus is that the treating substance adhered to the cords may foul certain operating elements of the apparatus. For example, when the cords are dip processed in a liquid, the liquid may harden and accumulate on roller surfaces, particularly those first contacting the cords after dipping. The adhered liquid may accumulate progressively to the point that the diameter of the roller appreciably increases. Without making adjustments elsewhere in the system, the cord tension thus becomes higher than intended. The adhered liquid may also cause a contamination problem.
To eliminate this problem, the heating temperature in prior art systems has been raised. It is also known to reduce the processing speed to increase the heating time and to extend the length of the heating ovens. However, certain temperatures produce optimum cord properties. By altering this temperature, the quality of the cord may be compromised. By reducing the processing speed, the capability of the apparatus is reduced. By extending the oven length, the overall size of the equipment may be increased, increasing costs and necessary operating space. Such modifications may make system inspection more difficult, which could ultimately result in a compromise in system safety.